1. Field of the Invention
The present invention relates to a drive control device and a drive control method for executing drive control of a motor connected with a plurality of inverters.
2. Description of the Related Art
In so-called “power steering” that assists control of a steering wheel using an electric motor, when a failure occurs in an inverter that supplies electric power to the motor, a wheel steerer person needs to perform a wheel operation by only his own power. However, in a case of a large vehicle, a torque is large and steering by only his own power requires a large force, which causes a large burden on the driver.
A plurality of inverters are connected to the electric motor, so that steering by only his own power can be prevented by, when a failure of one inverter occurs, causing another inverter to be operated. However, in order to enable a continuous operation of the motor by inverters other than the faulty inverter, a device for controlling a current conduction state, such as a switch is required between the faulty inverter and the motor (for example, see Japanese Patent Application Laid-open No. 9-275699 and Japanese Patent Application Laid-open No. 2011-45212).
As described in Japanese Patent Application Laid-open No. 9-275699 and Japanese Patent Application Laid-open No. 2011-45212, conventionally a switch and the like are provided between a faulty inverter and a motor, the switch is either in a short-circuit state or in an open state. Therefore, when a circuit including the motor and the inverter is changed from a short-circuit state to an open state, a large surge voltage is generated by an inductance component in the circuit, and insulation breakdown may occur in motor windings or the switch itself may be broken.
The present invention has been achieved in view of the above circumstances, and an object of the present invention is to provide a drive control device and a drive control method for suppressing generation of a surge voltage when a failure occurs in an inverter that drives a motor and driving of the motor is continued by other normal inverters.